Typically a wireless network (or at least each subnet of such a network) comprises a network facility, for example a Radio Network Controller (RNC), connected via a “back haul” network to a plurality of Base Stations (BTS). Each BTS communicates with terminals located in a cell centered at the BTS antenna via a wireless interface, such as IS95, IS2000 and 1xEV-DO. Typically each cell is divided into 3 sectors, each covered by a directional antenna and controlled by a Radio Network (RN) card within the BTS.
As many wireless terminals are mobile, the wireless network will not always know in which sector a terminal is located at any given time. Normally, the terminal informs the network of a change in its location only when it moves from one subnet (a relatively large geographical zone covering many sectors) to another subnet. Although it would be technically possible for the terminal to inform the network every time it moves between sectors, this is not practical, because the frequency of such updates would consume a large amount of processing and message transmission resources. Instead, in the past, wireless networks attempt to locate a mobile terminal only when there is traffic to send to the terminal, by “paging” the terminal in all the sectors of the subnet.
In order to better utilize the network resources, prior art methods have proposed paging a terminal only in the sector from which it had last transmitted a message to the network, and the surrounding sectors. Furthermore, to account for mobility, the prior art methods have proposed that the terminal sends location update messages (typically called Route Update (RU) messages) to the network to inform the network of its location after the terminal has moved a defined distance, or after it crosses a defined boundary. In either case, the terminal's location is considered to be the location (for example, the geographical coordinates) of a reference sector. The Reference sector is the sector with which the AT or terminal has registered, or to which the terminal last sent a RU message. Typically pages are sent to surrounding sectors to that lie within a defined distance from the reference sector. This distance is often called the RouteUpdateRadius (RUR). This distance defines the distance the terminal can move before the terminal needs to send its location update (RU). In other words, distance-based paging reduces the paging area by restricting paging to only a paging area determined by the RUR.
In such systems, the RNC typically determines which sectors (i.e., which RNs) should broadcast a page, based on their location, as well as the location of the serving/reference sector and the RUR for each terminal. The RNC then only sends paging messages to those RNs, which in turn broadcast the page over the wireless interface to the terminal. As stated, this conserves the wireless resources by restricting the broadcasting of paging messages to sectors in which the terminal is likely to be located.
However, such a described system adds to the processing burden of the RNC, which must now continuously determine the paging area for every terminal. The RNC must compute for each AT, which sectors in the subnet are within the paging area (defined by reference sector geographical coordinates, RUR and each and every sector's geographical coordinates). This would have to be done every time a RU message is received or each time a sector is added to or removed from the network. This increases the load on the RNC. Furthermore, this additional complexity presents challenges to scalability for a large network with large number of sectors and to a distributed network architecture or flat architecture.
It is, therefore, desirable to provide a distance-based paging mechanism that reduces the processing load on the RNC.